In the industry of security and protection, an analog video signal output by an analog video camera needs to be transmitted to a backend receiver through a coaxial cable, and an electric signal will be increasingly attenuated along with the increasing distance to be transmitted through the coaxial cable. Moreover, since the signals of different frequencies have different transmission delays for transmission through the coaxial cable, there will be the phenomenon of group delay, and high-frequency components will be attenuated rapidly, thus resulting in tailing of a video signal, the loss of a high-frequency signal, and other image distortion problems. Since the frequency of a normal standard-definition Composite Video Broadcast Signal (CVBS) ranges between 0 and 6 MHz, the distortion problem will be not obvious. However, for a high-definition analog video signal to be transmitted, since the frequency range of the signal is wider, ranging between 0 and 25 MHz and even between 0 and 50 MHz, the phenomenon of group delay and the attenuation of the high-frequency component will be more apparent.
There exists two general solutions of equalization compensation technology for an analog signal in the prior art:
1. At the signal receiver side, a video signal is compensated by a fixed gain value according to the attenuation of the received video signal, so as to achieve satisfactory amplitude of the signal. This solution may solve the attenuation problem of the amplitude of the signal, which especially effective for the standard-definition analog signal with a narrower bandwidth and a smaller difference between the attenuation of the highest frequency portion and the low-frequency portion of the signal. In addition, the phenomenon of group delay and attenuation of high frequency portion will be not obvious and possible to be improved effectively. But for the compensation of a high-definition analog video signal, merely using fixed amplitude gain may not meet the requirement of a practical application.
2. A solution using an integrated chip, which is also primarily for the markets of standard-definition analog signals. Since it operates in a fixed bandwidth and cannot change the frequency range of the signals according to applications, which is not applicable to high-definition video signals. Moreover since the cost of integrated chips is generally quite high, for cost-sensitive applications, a solution with a higher performance to price ratio is needed.
In summary, the solutions of equalization compensation technology for an analog video signal in the prior art is not applicable to a high-definition video signal.